In this project on human reactions to odors and irritants we plan to: 1) To measure olfactory sensitivity in a manner that optimizes reliability within constraints imposed by the clinical testing situation. Our work has entailed focal testing of promising psychophysical methodology that specifies both mean performance and variation in performance of individual subjects and it has entailed development of a computer-controlled olfactometer that runs the patient automatically and thereby eliminates limitations imposed by availability of personnel. We will continue these pursuits, both through studies of psychophysical methods and of alternate means of stimulus control and presentation. 2) To define the relationship between: 1) the mean and the variance of olfactory threshold distributions, 2) olfactory vs trigeminal thresholds, and 3) olfactory thresholds vs the growth of odor intensity above the threshold. Specification of such relationships can move the field of olfactory psychophysics toward sorely-needed quantitative predictions of potency. There are about 500,000 odorants and the ability to predict their potency is poor, despite a growing demand for such data. 3) To explore associations between psychophysical measures of nasal irritation and the negative mucosal potential. The negative mucosal potential may prove particularly useful for verification of symptoms of irritative hypersensitivity. But as an objective index of common chemical sensation in the nose its value goes beyond the pathological case. 4) To explore associations between mucosal pathology and the perception of irritation. Our previous research on irritation has focused more o the stimulus than on the host. We studied various series of chemicals in the hope that we could eventually predict the potency of volatile organic compounds as irritants. This has succeeded very well. As it turns out we are now far better prepared to study mucosal pathology. 5) To establish how limitations based upon quality discrimination determine performance in odor identification and memory. Within this context, we will explore the relative independence of a talent of discrimination that exists separately from sensitivity. People differ in absolute sensitivity and also differ somewhat independently in ability to discriminate quality. Our studies of epileptic patients suggest central neural involvement in discrimination. This work will extend of our previous work in which we developed a test of identification hat allows interpretation in terms of discriminability. We have also begun to understand interesting relationships among discrimination, identification, and odor memory, including priming.